UDID Faker is generall used to steal apps which we are not allowed to discuss on these forums.

Someone has managed to create a UDID faker which allows you to completely hide your iPhone’s identity and potential allow you to use other apps that people have paid for on the AppStore for free. The UDID of the iPhone is a unique code that every iPhone and iPod Touch has. With the UDID of an iPhone, you can spoof your devices UDID to be the same as that one to trick apps into thinking you have paid for the app and you will be able to use it for free.